Troubleshooting a Mazda CX-9 That Has Issues with the Smart Brake System After a 4 and 7-way Install

Updated 06/20/2023 | Published 06/19/2023

Products Featured in This Question

T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector

(164)

$58.98

Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires

(3397)

$121.25

Question:

We purchased a wiring harness for a 2019 Mazda CX9 from you with a 4 way and added the 7-way connector. We installed the harness and the braking system without any problems. We were informed to install a diode in line at the brake pedal wiring. Did we need to do this? Now we are getting codes that the Smart Brake Systemfoot that the car has is not functioning. Is this the diode causing the issue or is there a better place to wiring into the brake pedal system at a specific point to bypass and avoid the Smart Brake System the car has?

asked by: Mia C

Helpful Expert Reply:

I am not incredibly familiar with the Smart Brake System in your 2019 Mazda CX-9, but I do not see anything mentioning a diode when installing the T-One Vehicle Wiring Harness # 118278 and the Universal Installation Kit for Trailer Brake Controller # ETBC7.

A diode is designed to stop the reverse flow of current in an electrical circuit, so this could potentially be what is causing the issue with your Smart Brake System. Depending on how the system operates, it may need to be able to sense something from the brake that the diode is preventing.

When in doubt, you could reach out to Mazda because they should have more in depth knowledge of the Smart Brake System.

expert reply by: Scott S